1. Technical Field
The present invention relates to a semiconductor light emitting diode and to a method of manufacturing the semiconductor light emitting diode.
2. Description of the Related Art
Nitrides of group-III elements, such as gallium nitride (GaN), aluminum nitride (AIN), etc., exhibit high thermal stability and provide a direct transition type energy band structure, and are hence commonly used as materials in photoelectric elements for blue and ultraviolet light. In particular, blue and green light emitting diodes (LEDs) that use gallium nitride (GaN) are utilized in a variety of applications, examples of which include large flat panel displays, traffic lights, indoor lighting, high-density light sources, high-resolution output systems, and optical communication.
The structure of a nitride semiconductor LED may include a substrate, a buffer layer, a P-type semiconductor layer, an active layer, an N-type semiconductor layer, and electrodes. The active layer, where the recombination of electrons and electron holes may occur, can include quantum well layers, expressed by the formula InxGa1−xN (0≦x≦1), and quantum barrier layers. The wavelength of the light emitted from the LED may be determined by the type of material forming the active layer.
A brief description of a semiconductor LED based on the related art is provided as follows, with reference to FIGS. 1 and 2, which illustrate a method of manufacturing a semiconductor LED according to the related art.
As depicted in FIGS. 1 and 2, a semiconductor LED according to the related art may be composed of a sapphire substrate 1, for growing a GaN-based semiconductor material, as well as an N-type semiconductor layer 2, an active layer 3, and a P-type semiconductor layer 4, which are formed in the said order on the sapphire substrate 1. Portions of the P-type semiconductor layer 4 and active layer 3 may be removed, for example, by using a mesa etching process, to form a structure exposing portions of the upper surface of the N-type semiconductor layer 2.
A transparent electrode (see 60 in FIG. 4) and a P-type electrode (see 70 in FIG. 4) may be formed on the P-type semiconductor layer 4, while an N-type electrode (see 30 in FIG. 4) may be formed on the N-type semiconductor layer 2 exposed through the mesa etching process. This structure can be formed by growing the N-type semiconductor layer 2, active layer 3, and P-type semiconductor layer 4 sequentially on the substrate 1.
The structure described above can be implemented as a bulk-type substrate 1, which can be later divided into several unit LEDs. To facilitate the dividing process, division grooves 1a may be formed on one side of the substrate 1, as illustrated in FIG. 2. The process of forming such grooves la may be referred to as chip scribing. A typical chip scribing process may be performed using, for example, diamond. Afterwards, the chip can be divided, for example, by way of a breaking process, in which pressure is applied to divide the substrate 1. By dividing the chip through a breaking process after forming the division grooves 1a in straight lines across the substrate 1, the sides of the divided chips may have very little roughness, as illustrated in FIG. 3.
Thus, as illustrated in FIG. 3, total reflection may occur for certain ranges of light, due to the difference in refractivity between the inside and the outside of the chip and the incident angle of the light, so that some of the light emitted from the active layer 3 may not be emitted to the outside of the chip. That is, the total internal reflection within the chip may lower the light-emitting efficiency of the semiconductor LED. As such, a smooth section having little roughness may lower the light-emitting efficiency.